Como poner un boton con mensaje oculto

Bien lo primero es añadir un gadget javascrip y añadir este codigo

<center><div id="spoiler"><div><input value="Titulo del botoncito" style="width:200px ;font-size:12px;background-image: url(url del fondo del boton);-moz-border-radius: 10px; border-radius: 10px;margin:13px;padding:0px;border-style: 2px solid #ff9fcc;" type="button" onclick="if (this.parentNode.parentNode.getElementsByTagName(&#39;div&#39;)[&#39;show&#39;].style.display != &#39;&#39;) { this.parentNode.parentNode.getElementsByTagName(&#39;div&#39;)[&#39;show&#39;].style.display = &#39;&#39;; this.parentNode.parentNode.getElementsByTagName(&#39;div&#39;)[&#39;hide&#39;].style.display = &#39;none&#39;; this.innerText = &#39;&#39;; this.value = &#39;Hide Spoiler!&#39;; } else { this.parentNode.parentNode.getElementsByTagName(&#39;div&#39;)[&#39;show&#39;].style.display = &#39;none&#39;; this.parentNode.parentNode.getElementsByTagName(&#39;div&#39;)[&#39;hide&#39;].style.display = &#39;&#39;; this.innerText = &#39;&#39;; this.value = &#39;Show Spoiler!&#39;; }" />
<div id="show" style="display: none; background-color:transparent; background-repeat:repeat; margin: 0px;border-width:0px; padding:3px; width:90%">
<center><center>
Mensaje</center></center></div></div></div></center>
</div>

Y listo :))